<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<button>按钮1</button>
<button>按钮2</button>
<button>按钮3</button>
<button>按钮4</button>
<button>按钮5</button>
<script>
  var btns = document.querySelectorAll('button');

  for(var i = 0; i < btns.length; i++){
    btns[i].onclick = function () {
      for(var i = 0; i < btns.length; i++){
        btns[i].style.backgroundColor = '';
      }
      this.style.backgroundColor = 'pink';
    }
  }
</script>
</body>
</html>